Please, please, please put her in a preschool or pre-K program. I am an elementary school teacher and a mom of 3. I could literally write a paper on why early entry is wrong.
The short answer is that this decision isn't just about next year or even the next few years This decision is life long. Do you really want your 13 year old going off to high school with 19 year olds?That's what it will be.
I can go into the social issues that will develop in later elementary years,the issues that could arise from always being smaller and less developed than everyone in the class... There is just so much.
Wouldn't you rather she grew up thinking of herself as a leader, with self-confidence and wisdom?
One final point and then I'll get off my soap box. (You obviously hit a nerve with me.) No one cares when you are 35 when you started kindergarten. People look for others who are self-confident, hard-working, intelligent, kind, and positive.Keep your eye on the final result, a great human being.